Hi Team,
I have doubt what is the difference between getting elevated access to a user , using through adding the normal user to wheel group
and making an sudo file entry like user ALL=(ALL) PASSWD:ALL

Not sure what you are asking exactly. They both have the same result, one by using the default rule in /etc/sudoers to allow users in group wheel to use sudo, and the other by adding a rule to explicitly allow a specific user. Both are controlled by the rules in /etc/sudoers or /etc/sudoers.d/*.

On CentOS 6, just adding the user to group wheel does nothing special to them. They'll have no more access afterwards than they did before. Only if you edit /etc/sudoers with visudo and uncomment the line in there that gives group wheel access to group wheel will it make any difference.

CentOS 5 died in March 2017 - migrate NOW!
Full time Geek, part time moderator. Use the FAQ Luke